Gerald R. Smith

I study freshwater fish evolution in the late Cenozoic of North America.
Various fossil salmonids, minnows, suckers, sunfish, and sculpins are important
in Miocene, Pliocene, and (to a lesser extent) Pleistocene sediments of Washington,
Oregon, Idaho, Utah, Nevada, California, and Arizona, as well as adjoining states and
Mexico. When compared to the Recent faunas of Western U.S., these ancient fishes are
surprisingly more diverse and more specialized than their recent counterparts, reflecting
the destructive effects of Pleistocene climatic fluctuations.

Fish diversity and evolution are a function of stability of aquatic habitat,
which depends on consistent volume and temperature of water. Western habitats
have never benefited from the stability of aquatic habitats characteristic of
Eastern North America because active tectonic plate margins of the west have disrupted,
isolated, and elevated habitats causing high rates of extinction.